When LAN systems are checked for maintenance, it is insufficient simply to recognize its physical constitution, and it is also necessary to recognize (a) what terminal device (hereinafter often simply "terminal(s)") is connected to what position (how many meters it is distant from an end) of a LAN cable, and (b) whether the distance between terminals is as standardized. The information on (a) is information especially necessary to pinpoint the cause of faults.
As documents with which maintenance staffs recognize and manage such information, physical constitution diagrams of LAN have been manually prepared in the past.
Now, in LAN systems, it is relatively frequent to change a system configuration, e.g., to add or eliminate terminals and cables. For making such changes, it is cumbersome to manually adjust documents such as the physical constitution diagrams every time. There is also a possibility of making mistakes.
Moreover, such work is often carried out as secondary business, and hence is often not accomplished. Under existing circumstances, maintenance staff may only realize the importance of documents such as the diagrams for the first time when the LAN system causes problems.
A LAN system usually employing a collision detection type carrier sense multiple access CSMA/CD (IEEE 802.3) as an access control system is operated by algorithms with the assumption that some data transmitted from a plurality of terminals may collide with each other. In general, the occurrence of collision increases with increase in utilization, resulting in extreme lowering of the performance of LAN systems. However, it can only be assumed from the utilization of each terminal data transmitted from what terminal have caused or tend to cause collision. Especially in the case of collision due to defective physical layers of a LAN, it takes a lot of time to cut and divide the defective portions. Especially when the defective physical layers occur intermittently, it takes a long time to resolve the problems.
Electrical noise that may come over LAN cables also makes LAN throughput lower or makes a LAN system inoperable. With regard to such noise, no means is available for assuming the point where the noise has been generated, and it takes a long time to cope with it.
The present invention was made taking account of these problems. Accordingly, an object of the present invention is to provide a method and apparatus that can automatically collect the physical constitution information of LAN systems.
Another object of the present invention is to provide a system that can automatically prepare physical constitution diagrams of LAN systems by the use of such an apparatus.
Still another object of the present invention is to provide an apparatus that can ascertain the state of a LAN system with ease by specifying terminals having caused a collision of transmitted data when a LAN system is operated or detecting the position at which the noise is generated, and by keeping such terminals or noise-generated position on record even if it can not recognize the address of a packet transmitted over the LAN.